1. Field of the Invention
This invention relates to a controller for operating, on demand, small electric power generators, and more particularly to a controller for a small gasoline engine driven electric power generator, such controller designed to operate the electric power generator more efficiently, thereby conserving energy resources and extending the useful life of the generator.
2. Brief Description of the Prior Art
Controlling the operation of a gasoline-engine-operated electrical power generator in a variety of ways is known in the art. For the purposes of this description, the term "generator" is applied to the whole machine, and the term "alternator" is applied to the part of the machine which generates the alternating current (AC) power to be supplied externally. There are a number of patents which deal with automatic voltage regulators for a wide variety of generators for vehicles, aircraft, and others. Among these are U.S. Pat. Nos. 2,992,382; 4,184,083; 4,661,760; 4,749,944; 4,931,717; and 4,933,623. Also known are systems for controlling electric arc welders by starting the prime mover for the welding generator when the stinger is grounded to the work piece. Among these are U.S. Pat. Nos. 2,170,861; 2,237,894; 2,412,745; 2,419,276; 2,427,127; 2,480,635; 2,499,635; and 3,748,561. One of these, 2,412,745, was issued to David Packard, co-founder of the Hewlett-Packard Co.
U.S. Pat. No. 2,201,863 is an odd type of controller for a three phase wound rotor motor which is controlled in response to the number of times the load is cycled on and off.
U.S. Pat. No. 1,481,919, issued in 1924, is a rather complex system which is used with a 32 Volt DC farm power system in which a motor generator set driven by a 32 V DC motor and a generator having a "standard" voltage. The motor generator set also acts as a starter motor for the 32 V generator's engine.
U.S. Pat. No. 2,427,462 (issued Sept. 16, 1947 to H. F. Kaelin) discloses a system which is sensitive to a load on the generator. The Kaelin patent was applied for May 14, 1945, so that comparing it with the controller of the present invention is somewhat difficult because of the 50 year technology gap between the two, as well as because the two are designed with different system concepts in mind for starting a generator. The Kaelin system was designed to be used in conjunction with the "Startex" or similar system which is required to actually start a generator and allow it run as long as a circuit closure is maintained.
The schematic of '462 is redrawn in the accompanying FIG. 1 using modern terms, so that it can be explained easier. The apparatus of the Kaelin patent merely senses a load and closes a relay when there is a load present on the generator and activates the generator engine. When the load is removed, the generator stops. Without the supplemental "Startex" system, it has no capability of starting the generator's engine, let alone differently under different environmental conditions, and provides no delay in opening the contacts of the relay after the load is removed, and is devoid of a number of features which are desirable and essential in today's competitive industry. According to the text of the patent, it was intended to be used with the "Startex" or other controller which starts the generator engine when an external circuit is closed and stops it when the external circuit is opened. An explanation of the operation, according to the schematic of FIG. 1, follows.
One lead 3 of the coil of relay K1 is permanently connected to the hot terminal of the battery 5. When a load 4, 6, and/or 8 is placed upon the generator output load terminals 9, 9', the other lead 11 of the coil of K1 is connected through the closed contacts 5 and 6 of relay K2, to ground through the load, and thence back to the other terminal of the battery 5, energizing and closing the contacts 7 of relay K1. This starts the engine by means of the other controller with which it is associated (not shown). When the engine starts and the generator 13 produces output power, the coil of relay K2 is energized by the generator output power, connecting contacts 1 to 2 and 4 to 5. Current being supplied to the output load terminals 9, 9' flows through the primary of the current transformer 15 and produces an output which is connected to the coil of relay K1, holding it closed as long as there is a load on the generator power output load terminals 9, 9'. When all loads are removed, current through the primary of current transformer 15 ceases, and the secondary of current transformer can no longer supply power to the coil of K1 which then opens contacts 7 to deenergize the generator 13.
It should also be noted that it would be difficult or impossible to find a relay which would function optimally or even satisfactorily from an AC current transformer as well as from a low level DC source.